1. Field of the Invention:
The present invention relates to a dust seal device for a linear guide apparatus used in a machine tool, an industrial machine, and the like, and, in particular, to an improvement in an attaching structure of the under seals of the dust seal device.
2. Description of the Prior Art:
With reference to FIG. 3, a prior art linear guide apparatus generally includes an axially extended, elongated guide rail 1 and a slider 2 having a substantially inverted U-shaped cross section and movably straddling the guide rail 1. The guide rail 1 has ball rolling grooves 3 formed in both side surfaces. A main body 2A of the slider 2 has ball rolling grooves 5 formed in the inner surfaces of both side walls 4 so that the ball rolling grooves 5 respectively oppose the ball rolling grooves 3 of the guide rail 1 as shown in FIG. 4. A plurality of balls 6 are loaded in the opposed ball rolling grooves 3 and 5. The slider 2 is movable in an axial direction through rolling of the balls 6. With the movement of the slider 2, the balls 6 interposed between the guide rail 1 and the slider 2 are moved while rolling to an end of the slider main body 2A. In order to continuously move the slider 2 in the axial direction, it is necessary to circulate the balls 6. Accordingly, a through bore 7 is formed in each of the side walls 4 of the main body 2A as a ball return passage and, at the same time, end caps 2B having a substantially inverted U-shaped cross section are attached to opposite ends of the main body 2A. A pair of U-shaped curved paths 8 are formed in each of the end caps 2B, respectively, to bring the ball rolling grooves 3 and 5 in communication with the ball return passage 7. As a result, an endless ball circulating path is formed by the ball rolling grooves 3 and 5, the curved paths 8, and the ball return passages 7.
When foreign matter, such as dust, chips, cuttings, and the like, intrude into a gap between the guide rail 1 and the slider 2 straddling the guide rail 1 and are deposited on the ball rolling grooves 3 and 5 and the like, the smooth movement of the balls 6 is disturbed. Accordingly, a side seal 10 is usually attached by small screws n to an outer end surface 2c of each end cap 8 to prevent the foreign matter from intruding from opposite end portions of the slider 2. At the same time, under seals 11, FIG. 5, are attached to the lower surfaces of the slider 2 to seal gaps between the side surfaces 1b of the guide rail 1 and the lower surfaces of the slider 2 to thereby prevent foreign matter from entering through the lower gaps.
FIG. 5 shows an example of a prior art structure for attaching the under seals 11. Each under seal 11 is an elastic sheet of a rectangular strip shape. Each under seal 11 has a length substantially equal to the length of the slider main body 2A and a width a little larger than the width of the lower end surface 12 of the slider main body 2A. Three fixing bores 13 are formed in the under seal 11 at spaced intervals in an axial direction. On the other hand, rivet bores 14 corresponding to the fixing bores 13 are formed in each lower end surface 12 of the slider main body 2A. The under seal 11 is applied to the end surface 12 of the slider main body 2A and fixed by inserting rivets 15 through the fixing bores 13 and into the rivet bores 14. Each lower end surface 16 of the end cap 2B is flat. An inner edge 17 of the fixed under seal 11 is slidably in contact with the side surface 1b of the guide rail 1 to achieve the sealing of the lower side of the slider 2.
However, in such a prior art dust seal device, or a dust seal structure of the under seals of a linear guide apparatus, since the under seals are fixed by riveting, the following problems are encountered:
A process for forming the rivet bores 14 in the lower end surface 12 of the slider main body 2A is required. Thus, the number of working processes is increased.
At the time of fixing the under seals 11, labor for inserting the rivets 15 is needed. Such labor is hand work such that the manufacturing efficiency is very low. Thus, the number of assembling processes increases.
Since rivets are used, there is a concern for the reliability in securing the under seals 11.
Since the length of the under seal 11 is made equal to that of the slider main body 2A and the areas of the lower surfaces of the end caps 2B are not covered by the under seal 11, sealing is incomplete.
In contrast, another prior art structure was proposed as shown in FIG. 6. In this structure, each under seal 11 is mounted by fitting opposite ends of the under seal 11 respectively into slittings 18 formed in lower portions of the end caps 2B. In this structure, rivets are not used and the mounting of the under seal 11 is easy. However, since the end caps 2B are injection mold products of a synthetic resin, the strength of the slittings 18 for fixing the under seal 11 is weak and there is a concern for the safe operation of the apparatus. Furthermore, since the slitting 18 cannot be formed to extend completely to an axial outer end of each end cap 2B, the sealing of opposite end portions of the under seal 11 is incomplete.